1. Field of the Invention
The invention relates to a tool head for securing a tool in a machine tool. The tool head comprises a stationary spindle bearing housing, a spindle rotatably supported in the spindle bearing housing, a modular tool changing insert configured to receive the tool and exchangeably arranged on the spindle or a holder of the spindle.
2. Description of the Related Art
The economic use of cutting tools on machine tools requires the supply of cooling medium (coolant) to the cutting edge in order to cool and lubricate the cutting edge and to remove the cuttings that are produced. This is realized by means of diverse cooling medium supply devices such as sealing lip systems, gap seals as well as axial face seals. All of these known configurations have in common that the supply of the cooling medium takes place directly in the rotating spindle of the machine tool or in the driven tool or is realized by means of an auxiliary device. The supply of the cooling medium is carried out either in front of, behind or between the bearing of the spindle relative to the housing. The very complex process of machining by cutting, depending on the application, requires different pressure stages for an optimal supply of the cooling medium to the cutting edge of the tool. In the case of deep drilling operations, the required cooling medium pressure can even be between 20 and several 100 bar.
In order to achieve an additional productivity increase, the use of modular tool systems of the aforementioned kind has been promoted in recent years. The principal idea in this connection is that the tool is not received directly at the forward end of the spindle or of a holder on the spindle but that a tool changing insert is exchangeably arranged as a module on the spindle or the holder. This tool changing insert then actually receives the tool.
These modular systems have the advantage that the cutting tools can be preadjusted and introduced into the tool changing insert externally to the machine tool. As a result of the configuration of such modular tool changing systems, the changing of the tool changing insert into the spindle or the holder is carried out such that the tool change generally is carried out significantly faster and, more importantly, with already pre-adjusted cutting tools.
The tool changing systems however have disadvantages in some respects, as a result of their clamping systems, in regard to the entire tool length. These disadvantages in regard to the tool length have an effect primarily in the case of machines with restricted available space. When combining, for example, in the case of driven tools, the tool with the afore described modular tool changing receptacle, i.e., the tool changing insert, and an internal cooling medium supply device, very significant length problems can result which can only be resolved by measures in regard to the configuration of the machine tool. In the case of an internal cooling medium supply, the supply of the cooling medium begins at the spindle bearing housing and continues via the spindle into the tool changing insert and from there to the tool. The cooling medium supply in these known modular systems employing an additional tool changing insert, is such that the disadvantage of these modular tool systems with respect to the configurational length is even more pronounced by installing the inner cooling medium supply device.
A further disadvantage of the known inner cooling medium supply device, arranged between, before or behind the bearing, is that in the case of defects or system—caused leakage cooling medium can penetrate into the driven tool. Finally, with the known internal cooling medium supply device it is not possible to use optimal sealing strategies because they cannot be integrated within the tool head for configurational reasons or functional considerations.